A compressor, which is used in an automotive air conditioning system, is usually mounted on the engine of the automobile through a suitable mounting bracket. In the above structure, if strength of the mounting bracket is insufficient relative to the weight of the compressor, vibration which occurs on the compressor on the basis of vibration of the engine is enlarged by the mounting bracket, and may achieve a huge level. The enlargement of vibration of the compressor may produce the point of resonance thereof with respect to vibration of the engine within the range of usual rotational engine speed.
Excess vibration may reduce the durability of the compressor. Moreover, the mounting bracket may be broken by fatigue. In the prior art to reduce the above problem, it is known to increase the strength and/or stiffness of the mounting bracket by increasing the thickness of the mounting bracket or the number of reinforced ribs thereon.
However, even though such a mounting bracket is used, the technique of increasing the strength and/or stiffness of the mounting bracket does not significantly contribute to reducing compressor vibration because vibration of the mounting bracket is increased due to increasing the weight thereof.
Moreover, it may be impossible to take the space in an engine room to mount such a mounting bracket.
In addition, if an engine produces a large vibration or a compressor resonates with an engine, even though the strength of a mounting bracket is greatly increased, the compressor vibration level may still be large.